U.S. patent number 4,442,270 [Application Number 06/464,804] was granted by the patent office on 1984-04-10 for thermosetting powder coating compositions.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Paul McBride, David T. Passmore, Willis C. Wooten.
United States Patent |
4,442,270 |
Passmore , et al. |
April 10, 1984 |
Thermosetting powder coating compositions
Abstract
Disclosed are crystalline polyesters having low melt
viscosities, and thermosetting compositions comprising these
polyesters. The compositions are especially useful as powder
coatings. At least 40 mole percent of the acid moiety is a
terephthalic or isophthalic acid moiety, and the polyester contains
as moieties of the dihydric alcohol about 40-100 mole percent
1,6-hexanediol, the polyester being further characterized as having
a molecular weight of about 700-3000, a melt viscosity of about
50-3000 cps at 160.degree. C. and a hydroxyl number of about
30-160.
Inventors: |
Passmore; David T. (Golborne,
GB2), Wooten; Willis C. (Kingsport, TN), McBride;
Paul (Crescent Green, GB2) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
26958979 |
Appl.
No.: |
06/464,804 |
Filed: |
February 8, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
278228 |
Jun 29, 1981 |
4387214 |
|
|
|
Current U.S.
Class: |
525/440.02;
524/904; 525/438; 525/443; 528/296 |
Current CPC
Class: |
C08G
63/181 (20130101); C08G 63/20 (20130101); C09D
167/00 (20130101); Y10S 524/904 (20130101); C08G
2150/20 (20130101) |
Current International
Class: |
C08G
63/00 (20060101); C08G 63/181 (20060101); C08G
63/20 (20060101); C09D 167/00 (20060101); C08L
063/00 (); C08L 061/28 (); C08L 067/02 () |
Field of
Search: |
;528/296
;525/440,443,438 ;524/904 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Chemical Abstracts, 90:40330x, 1979..
|
Primary Examiner: Lieberman; Allan
Attorney, Agent or Firm: Stevens; John F. Reece, III; Daniel
B.
Parent Case Text
This application is a division of Ser. No. 278,228, filed June 29,
1981, now U.S. Pat. No. 4,387,214.
Claims
We claim:
1. A thermosetting composition comprising
(a) a linear saturated crystalline polyester of an acid moiety and
a moiety of a dihydric alcohol, at least 40 mole percent of the
acid moiety being a terephthalic or isophthalic acid moiety, said
polyester containing as moieties of the dihydric alcohol at least
40 mole percent 1,6-hexanediol, said polyester being further
characterized as having a molecular weight of about 700-3000, a
melt viscosity of about 50-3000 cps at 160.degree. C. and a
hydroxyl number of about 35-160, and
(b) from about 10 to about 40%, based on the weight of said
polyester, of a curing agent which is reactive with hydroxyl groups
to crosslink said polyester.
2. A thermosetting composition comprising
(a) a linear saturated crystalline polyester of an acid moiety and
a moiety of a dihydric alcohol, at least 40 mole percent of the
acid moiety being a terephthalic acid moiety, said polyester
containing as moieties of the dihydric alcohol at least 40 mole
percent 1,6-hexanediol, said polyester being further characterized
as having a molecular weight of about 1000-2000, a melt viscosity
of about 50-1000 cps at 160.degree. C. and a hydroxyl number of
about 50-125, and
(b) from about 10 to about 40%, based on the weight of said
polyester, of a curing agent which is reactive with hydroxyl groups
to crosslink said polyester.
3. A composition according to claim 1 wherein said polyester
contains moieties of at least one other glycol selected from the
group consisting of ethylene glycol, 1,4-butaneidol, neopentyl
glycol and 1,4-cyclohexanedimethanol.
4. A composition according to claim 2 wherein the glycol is
1,4-butanediol.
5. A composition according to claim 1 wherein the molecular weight
of said polyester is about 1000-2000.
6. A composition according to claim 1 wherein the hydroxyl number
of said polyester is about 50-125.
7. A composition according to claim 1 wherein said curing agent is
selected from the group consisting of blocked isocyanates and
melamines.
8. A composition according to claim 6 wherein said curing agent is
an alkoxymelamine wherein the alkoxy group contains from 1 to 8
carbon atoms.
9. A composition according to claim 1 which further contains a
catalyzingamount of an acid catalyst.
10. A composition according to claim 8 wherein said catalyst is
present in an amount of from about 0.01 to about 5%, based on the
weight of the polyester.
11. A composition according to claim 1 in particulate form of a
size suitable for coating as a powder.
12. A composition according to claim 8 in particulate form of a
size suitable for coating as a powder.
13. A thermosetting powder composition comprising
(a) a linear saturated crystalline polyester of an acid moiety and
a moiety of a dihydric alcohol, at least 40 mole percent of the
acid moiety being a terephthalic acid moiety, said polyester
containing as moieties of the dihydric alcohol at least 40 mole
percent 1,6-hexanediol and a second glycol selected from the group
consisting of ethylene glycol, 1,4-butanediol, neopentyl glycol and
1,4-cyclohexanedimethanol, said polyester being further
characterized as having a molecular weight of about 1000-2000, a
melt viscosity of about 50-1000 cps at 160.degree. C. and a
hydroxyl number of about 50-125,
(b) from about 10 to about 40%, based on the weight of said
polyester of a curing agent which is reactive with hydroxyl groups
to crosslink said polyester, and
(c) a catalyzing amount of an acid catalyst.
Description
TECHNICAL FIELD
This invention relates to thermosetting polyester compositions
especially adapted for use as powder coatings.
BACKGROUND ART
Thermosetting polyesters have long been used in surface coatings.
Hydroxyl and carboxyl groups are most frequently utilised to impart
reactive functionality to these resins. In the area of powder
coatings, hydroxyl-functional polyesters are usually cured using
alkoxymelamine, anhydride or blocked isocyanate crosslinkers.
Typical of the hydroxylated polyesters known for use in coating
formulations are those derived from various combinations of
terephthalic acid, neopentyl glycol, cyclohexanedimethanol, and
polyols such as trimethylolpropane. Such polyesters are generally
amorphous and have relatively high melt viscosities at fusion
temperatures. These resins, at a typical fusion temperature of
160.degree. C., have melt viscosities in excess of about 6500 cps,
and often in excess of 10,000 cps.
The high melt viscosity tends to limit the flow of the molten
coating and hence adversely affects the smoothness and gloss of the
finished coating. Cure speed of these resins depends upon the type
of crosslinking agent used, but none are recommended for use at
cure schedules less than 160.degree. C. for 35 minutes. Below these
recommended temperatures, the coatings generally have a poor
appearance and poor physical properties are obtained.
Patents of interest include U.S. Pat. No. 4,094,721 which discloses
copolyesters of terephthalic acid, 1,4-butanediol and
1,6-hexanediol. These copolyesters, however, have a relatively high
molecular weight and a relatively high melt viscosity, which
satisfies the requirements for the intended purpose, i.e., a fusion
adhesive. The high melt viscosity tends to limit the flow of the
molten coating and hence adversely affects the smoothness and gloss
of the finished coating.
DISCLOSURE OF THE INVENTION
The crystalline polyesters described herein have several advantages
properties which render them superior to the conventional amorphous
thermoset polyesters currently used in powder coatings, i.e.,
(a) The crystalline polyesters of a given molecular weight tend to
have lower melt viscosities than those normally associated with the
amorphous polyesters of similar molecular weight which are
currently used in powder coatings. This means that powder coatings
based on these crystalline, thermoset polyesters generally flow
better on fusion, resulting in less orange peel and smooth coatings
having high gloss.
(b) The crystalline polyesters react more rapidly with the blocked
isocyanate crosslinker than would be expected. This results in
coating formulations which can cure at temperatures as low as
150.degree. C. With suitable curing agents, even lower curing
temperatures might be achieved.
(c) The crystalline polyesters, when incorporated into powder
formulations cured with blocked isocyanate crosslinker, give
finished coatings having outstanding physical properties.
(d) The crystalline nature of the resins enhances their
anti-blocking properties at room temperature. Amorphous resins
having similar molecular weight distribution to the crystalline
copolyesters would be expected to undergo more pronounced blocking
on storage at ambient conditions.
(e) The crystalline polymers impart a more rapid build-up of
physical properties to the coatings during fusion compared to
currently used commercial resins.
(f) The composition of the inherent low viscosity of the
crystalline resins and the high level of physical properties they
impart to the final coating, enables significantly higher filler
concentrations to be used in formulations based on crystalline
resins compared to formulations containing amorphous resins of
similar molecular weight distribution.
The present invention provides copolyesters particularly useful in
thermosetting compositions, more particularly, thermosetting powder
coating compositions such as might be used as automobile coatings.
The copolyesters are linear, saturated and crystalline, having
functional hydroxyl groups, acid moieties and dihydric alcohol
moieties, at least 40 mole percent of the acid moieties being
terephthalic or isophthalic acid moieties. The polyester contains
as moieties of the dihydric alcohol about 40-100 mole percent,
1,6-hexanediol and 0 to about 60 mole percent of at least one
glycol selected from the group consisting of ethylene glycol,
1,4-butanediol, neopentyl glycol, and
1,4-cyclohexanedimethanol.
According to this invention, there is provided a crystalline
polyester which is especially useful in the production of
thermosetting powder coating compositions, such as might be used as
automobile coatings. The polyester may be described generally as a
linear, saturated, crystalline polyester of acid moieties and
dihydric alcohol moieties. The polyester is futher characterized as
having a number average molecular weight of about 700-3000,
preferably about 1000-2000. Also, the polyesters have a melt
viscosity of about 50-3000 cps at 160.degree. C. The hydroxyl
number is in the range of about 30-160, preferably about
50-125.
The polyesters described herein have the unique ability to form
thermosetting powder coatings which have low melt viscosities,
thereby allowing the powder to flow out to form a smooth coating
prior to setting up. On the other hand, the powder is more
resistant to caking than amorphous polyesters of similar molecular
weight distribution.
The copolyesters of the invention contain terephthalic or
isophthalic acid moieties. These moieties can be supplied by the
usual terephthalic or isophthalic moiety sources, e.g.,
terephthalic acid, terephthaloyl chloride and the mono- and dialkyl
esters of terephthalic acid. Thus, the term "terephthalic moiety"
or "terephthalic acid moiety" is to be considered as including
those moieties supplied by the acid chloride or a mono- or diester.
The polyester contains terephthalic or isophthalic acid in an
amount of at least 40 mol %, based upon the acid moieties. Stated
differently, the copolyester of the invention is a terephthalic or
isophthalic acid copolyester in which from 1 to 60 mol percent of
terephthalic or isophthalic acid moieties are replaced, if desired,
by a second acid moiety.
If a portion of the terephthalic or isophthalic acid moiety is
replaced by a second acid moiety, it is replaced by a saturated
aliphatic dicarboxylic acid having terminal carboxylic acid groups
having from 4 to about 34 carbon atoms between the two carboxyl
groups. Preferably, the saturated aliphatic dicarboxylic acid
contains between 4 and 8 carbon atoms between the carboxyl groups.
Examples of aliphatic dicarboxylic acids contemplated include
adipic, azelaic or sebacic acid or mixtures thereof.
The diol component of the copolyesters of the invention preferably
comprises one or more glycols selected from ethylene glycol,
1,4-butanediol, neopentyl glycol, or 1,4-cyclohexanedimethanol and
1,6-hexanediol where the combined quantities of these diols
constitute all of the diol component.
With respect to the aliphatic or the aromatic dicarboxylic acids,
polyester forming derivatives can be used in the preparation of the
polyester, especially the mono- or dialkyl esters of the named
dicarboxylic acids, especially C.sub.1 -C.sub.4 mono- or dialkyl
esters, particularly the dimethyl esters.
In a preferred embodiment of the invention, part of the
dicarboxylic acid or glycol moieties of the polyester are replaced
by polyols or polybasic acids (having three or more functional
groups) to enhance crosslinking. The preferred polyfunctional
material is trimethylolpropane. Other suitable polyols include
trimethylolethane, pentaerythritol, glycerine, sorbitol, etc.
Suitable polybasic acids include trimellitic anhydride. If such
polyfunctional materials are used, it is preferred that they be
used in amounts of between about 0.1 and about 12 mole percent.
The polyesters according to this invention are prepared using
conventional esterification techniques well known in the art. Some
excess glycol is used, and the reaction is such that the polymer is
of a relatively low molecular weight, i.e., about 700-3000. The
excess glycol and low molecular weight provide for the functional
hydroxyl groups in the polymer for crosslinking, thereby making the
polymer thermosetting.
Suitable curing or crosslinking agents for use with thermosetting
resins containing functional hydroxyl groups, i.e., the polyester
disclosed herein, are well known in the art. Such curing agents
include blocked isocyanates, melamines and polyfunctional epoxy
compounds containing at least two glycidyl groups. An example of a
preferred isocyanate is Huls B1530, a caprolactam-blocked
polyfunctional isocyanate. Suitable melamines include
alkoxymelamine wherein the alkoxy group contains 1 to 8 carbon
atoms. Specific examples are Cymel 300 and Cymel 303
hexamethoxymethyl melamines. The curing agents are used in amounts
of between about 10% and 40%, preferably 15-30%, based on the
weight of polyester. By blocked curing agents, it is meant that the
curing agent is temporarily deactivated or neutralized so as to
allow the powder to flow out and form a smooth coating prior to
crosslinking. Blocked curing agents and catalysts are well known in
the art, e.g., U.S. Pat. No. 3,842,021. In any case, it is
preferred that the curing agent be blocked, so as to allow complete
flow-out of the powder to eliminate or reduce orange-peel and
thereby produce a smooth coating prior to the coating setting
up.
Although the thermosetting composition containing the polyester and
curing agent has been found to cure without the use of a catalyst
at temperatures as low as about 150.degree. C., it is sometimes
desirable to use a catalyst. Suitable catalysts are well known in
the art and include acid catalysts such as p-toluenesulfonic acid
for melamines and dibutyl tin dilaurate for isocyanates.
The thermosetting composition may also contain a suitable
plasticizer. The plasticizer must be sufficiently compatible to
avoid a sticky formulation. Suitable plasticizers include dioctyl
phthalate, dibutyl phthalate, butyl benzyl phthalate, dicyclohexyl
phthalate, 2,2,4-trimethylpentanediol-1,3-monoisobutyrate
monobenzoate, trioctyl trimellitate, an ester derived from
neopentyl glycol and adipic acid, or the like.
Conventional stabilizers, such as Irganox 1093, a product of
Ciba-Geigy, may be used in small amounts to prevent discoloration,
etc. Also, conventional dyes or pigments such as R-100 titanium
dioxide pigment marketed by Du Pont may be used. Conventional flow
aids, fillers, preservatives, etc., may also be used.
The components of the composition according to this invention may
be mixed by dry blending in a mixer or blender (e.g., a Waring
Blender), followed by compounding in a Buss Ko-Kneader, Wearner and
Pfleiderer or similar extrusion mixing machine at
90.degree.-140.degree. C. and 30-100 r.p.m., granulating, grinding
and then screening to obtain a 150 mesh powder for coating. Also,
the polyester pigment and stabilizer, if used, may be extruded at
about 200.degree. C., then mixed with the crosslinking agent,
catalyst, and plasticizer (if used) in a Banbury mixer, a
combination of a Banbury mixer and roll mill, a roll mill alone or
an extruder at a temperature of between about 90.degree. C. and
150.degree. C. Alternately, all the components may be dissolved in
a solvent such as methylene chloride (at about 20 weight percent
solids) and spray dried at a chamber temperature of about
50.degree. C. by well-known techniques.
The powdered composition may be deposited on the substrate by use
of a powder gun, by electrostatic deposition or by deposition from
a fluidized bed or by other well-known methods of powder
deposition. After deposition the powder is heated to a temperature
sufficient to cause its particles to flow and thus fuse together to
form a smooth, uniform, continuous, uncratered coating on the
substrate surface.
The following examples are submitted for a better understanding of
the invention. In the examples, the physical properties of the
coatings are determined as follows:
Peel Adhesion
Because powder coatings generally have superior adhesion properties
to wet paints, the adhesion tape test commonly used for wet systems
is often abandoned in favor of the more demanding peel adhesion
test. In this test a scalpel is used to cut two intersecting lines,
each about 2 cm. long, at about 60.degree. to one another. The tip
of the scalpel is used to try to lift the coating from the
substrate. If the coating can be removed easily, the test result is
rated as "fail". If the coating cannot be removed from the
substrate, except by scraping, then a "pass" is recorded.
Acetone Resistance
The softening of the coating caused by acetone being applied to the
surface is determined.
Caking Test
100 mls of powder are poured into a 27 mm diameter measuring
cylinder which is then placed in a forced air oven at a constant
temperature of 40.degree. C. The powder is examined for loss of
free-flowing properties after 24, 48, 72, 96 and 168 hours.
Orange Peel
The orange peel effect is rated on a scale from 1 (severe orange
peel) to 8 (no orange peel) using a set of standards panels for
comparison. At the lower levels of orange peel, in the range of
ratings 7 to 8, a set of ten standard panels is used to give more
accurate assessment, and panels in this range are rated to an
accuracy of two figures, e.g., 7.1, 7.5, etc.
Impact Strength
Impact strength is determined by using a Gardner Laboratory, Inc.,
Impact Tester. A weight is dropped within a slide tube from a
specified height to hit a punch having a 5/8 inch diameter
hemispherical nose which is driven into the front (coated face) or
back of the panel. The highest impact which does not crack the
coating is recorded in inch-pounds, front and reverse.
Flexibility
The test panel is bent over a period of 15 seconds, using a Gardner
Laboratory, Inc., conical mandrel of specified size, according to
ASTM D-522. A pass or fail is recorded.
Gloss
Twenty degree and sixty degree gloss are measured using a gloss
meter (Gardner Laboratory, Inc., Model GG-9095) according to ASTM
D-523.
Pencil Hardness
The pencil hardness of a coating is that of the hardest pencil that
will not cut into the coating. The procedure for preparing the
truncated cone pencil lead and carrying out the test is given in
the National Coil Coaters Association Technical Bulletin No. II
(Aug. 12, 1968). Results are expressed according to the following
scale:
(softest) 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H
(hardest)
Coating Thickness
The coating thickness is determined using a Fischer Instrumentation
(GB) Ltd. Permascope Model ES 8e 3K 4.
Fusion of the Coating
Test panels are placed in a Gallenkamp forced air oven and fused at
a specified temperature for a specified time. The fused coatings
are then hung on a bar to cool at room temperature.
Examples 1 and 2 which follow illustrate typical techniques for
forming the polyesters according to this invention.
EXAMPLE 1
Two thousand thirty seven g. (10.5 moles) of dimethyl
terephthalate, 1062 g (9 moles) of 1,6-hexanediol, 270 g (3 moles)
of 1,4-butanediol and 2 g of dibutyl tin oxide are heated under
nitrogen in a conventional single stage reaction. Cook log is shown
below.
______________________________________ Process Time (Hr.) Temp.
.degree.C. Distillate (ml) ______________________________________ 6
0-200 -- approx. 2 200-225 820 (Theory = 840) Resin Properties
Molecular Wt. = 1,338 Hydroxyl No. = 88 Acid No. = <1 Melt
viscosity at 160 .degree. C. = 215 cp.
______________________________________
EXAMPLE 2
Seventeen hundred g. of dimethyl terephthalate, 1216 g.
1,6-hexanediol, 48 g trimethylol propane and 3 g of dibutyl tin
oxide are heated under nitrogen in a conventional single stage
process according to the following cook log.
______________________________________ Process Time (hr) Temp.
(.degree.C.) Distillate (ml) ______________________________________
0 22 -- 1.25 140 100 1.5 165 310 2.0 195 630 2.5 200 670 3.5 200
680 6.5 180 680 (Theory = 710) Resin Properties Hydroxyl No. = 81
Acid No. = <1 Molecular Wt. = 1200 (Theory = 1500)
______________________________________
Other resins prepared in a conventional manner, similar to Examples
1 and 2, are given in Table 1, Examples 3-12 and 75-82. Dimethyl
terephthalate is used in all examples as the dicarboxylic acid.
1,6-Hexanediol is used with other glycols as noted.
TABLE 1 ______________________________________ Melt Viscosity*
Softening Ex. % 1,4- Molecular Hydroxyl (cps at Range No.
Butanediol Wt. No. 160.degree. C.) .degree.C.
______________________________________ 3 0 1174 73 150 99-144 4 0
2100 62 362 118-156 5 25 820 82 65 81-120 6 25 1338 88 215 88-136 7
50 860 122 84 96-154 8 50 1018 62 257 114-160 9 75 894 100 760
92-190 10 75 1342 INSOL -- 158-200 11 0 1200 81 632 80-120 12 0
2200 81 906 96-138 ______________________________________ *The
polyester of Ex. 11 is modified with 4 mole % trimethylolpropane.
Th polyester of Ex. 12 is modified with 12 mole %
trimethylolpropane.
Direct comparison of the melt viscosities at 160.degree. C. of
selected crystalline resins relative to currently used commerical
resins (R, S and T) of comparable molecular weight and hydroxyl
number is made in Table 2. These results clearly show the very low
melt viscosity of the crystalline resins relative to the
conventional polymers.
TABLE 2 ______________________________________ Molecular Hydroxyl
Melt Viscosity Resin Wt. No. (cps at 160.degree. C.)
______________________________________ From Ex. 4 2100 62 362 From
Ex. 12 2200 81 906 R 2400 56 >10,000 S 1850 59 6,700 T 2700 62
>10,000 ______________________________________
The properties of the crystalline resins make them particularly
suited for use in powder coatings, both in high filler content auto
primer surfacer formulations and high gloss top coat formulations
for a wide variety of metal products, e.g., applicances, furniture,
cycles, etc. The performance of representative resins in powder
primer surfacers is shown in Examples 13-56. Included for
comparison is the performance of formulations based on a commercial
polyester. The crosslinking agent used in all cases is a
caprolactam-blocked polyfunctional isocyanate.
TABLE 3 ______________________________________ CRYSTALLINE
HYDROXYLATED POLYESTERS IN AUTO PRIMER SURFACER FORMULATIONS Parts
by Weight COMPONENT A B C D E F
______________________________________ Resin S 80 -- -- -- -- --
From Ex. 4 -- 76.7 -- -- -- -- From Ex. 6 -- -- 69.6 -- -- -- From
Ex. 8 -- -- -- 76.7 -- -- From Ex. 11 -- -- -- -- 71.4 -- From Ex.
12 -- -- -- -- -- 71.4 Crosslinking Agent 20 23.3 30.1 23.3 28.6
28.6 Filler 90 90 90 90 90 90 Plasticizer 5 5 5 5 5 5 Polymerized
Debutanized 5 5 5 5 5 2.5 Aromatic Hydrocarbon Resin Flow Modifier
1 1 1 1 1 1 Volatiles Release 0.5 0.5 0.5 0.5 0.5 0.5 Agent 5:1
Resin H:Catalyst -- -- -- -- -- 3.0 Titanium Dioxide 10 10 10 10 10
10 Mix Temperature (.degree.C.) 120 110 100 90 120 120
______________________________________
All of the primer surfacer formulations readily cured at
163.degree. C. for 45 minutes to give finishes having low orange
peel. However, the formulations based on the crystalline resins
gave physical properties superior to those obtained using the
commercial resin. Furthermore, the crystalline polyester-based
formulations maintained their high performance even on curing at
150.degree. C. for 45 minutes. On the other hand, the control
primers completely lost their physical properties on curing at this
lower temperature. This clearly demonstrates the novel low
temperature cure properties of the crystalline polyesters.
Two of the crystalline polyesters (Example 8 and Example 11) give
high gloss coatings of excellent physical properties even on curing
at 180.degree. C. for 5 minutes. Under these cure conditions, the
commercial resin gives low gloss finishes having poor physical
properties.
Examples 13-56 are examples of physical properties of Formulations
A-F in a coating. Fusion time is 45 minutes. The following table
applies to these examples.
______________________________________ Examples Fusion Temperature
Formulation ______________________________________ 13-15 163 A
16-19 163 B 20-24 163 C 25-29 163 D 30-33 163 E 34-36 163 F 37-38
150 A 39-42 150 B 43-45 150 C 45-50 150 D 51-53 150 E 54-56 150 F
______________________________________
__________________________________________________________________________
Thick- Orange Impact Resistance ness 20.degree. Peel Pencil Peel
Front Reverse Ex. m Gloss Adhesion Hardness Rating (in. lbs.) (in.
lbs.) Flexibility
__________________________________________________________________________
13 21 36 Pass 3H 2 >160 140 7 mm Cracking 14 34 40 Pass 3H 6-7
80 60 11 mm Cracking 15 49 40 Pass 2H 7 60 8 27 mm Cracking 16 18
21 Pass 2H 5 >160 >160 No Cracking 17 31 17 Pass HB 7 >160
>160 No Cracking 18 39 17 Pass B 7 >160 >160 No Cracking
19 64 17 Pass B 7 >160 >160 No Cracking 20 18 40 Pass F 7.1
>160 >160 No Cracking 21 27 45 Pass HB 7.1 >160 >160 No
Cracking 22 34 52 Pass B 7.1 >160 160 No Cracking 23 50 53 Pass
B 7.5 >160 >160 No Cracking 24 70 51 Pass B 7.7 >160
>160 No Cracking 25 21 39 Pass H 7 >160 >160 No Cracking
26 36 42 Pass HB 7.1 >160 >160 No Cracking 27 48 34 Pass HB
7.1 >160 >160 No Cracking 28 63 45 Pass HB 7.6 >160
>160 No Cracking 29 71 45 Pass HB 7.6 >160 >160 No
Cracking 30 20 15 Pass 2H 4 >160 >160 No Cracking 31 30 23
Pass HB 7 >160 >160 No Cracking 32 49 30 Pass HB 7.3 >160
>160 No Cracking 33 68 27 Pass HB 7.5 >160 >160 No
Cracking 34 23 5 Pass 2H 2 >160 >160 No Cracking 35 39 6 Pass
2H 3 >160 >160 5 mm Cracking 36 55 5 Pass 2H 4 >160 80 15
mm Cracking 37 23 Pass 2H 40 8 38 72 Pass HB 8 <2 39 24 21 Pass
F 5 >160 >160 No Cracking 40 37 19 Pass B 7 >160 >160
No Cracking 41 45 20 Pass B 7 >160 >160 No Cracking 42 66 18
Pass B 7 >160 >160 No Cracking 43 19 40 Pass F 7 >160
>160 No Cracking 44 50 51 Pass B 7.7 >160 >160 No Cracking
45 66 53 Pass B 7.8 >160 >160 No Cracking 46 18 41 Pass H 5
>160 >160 No Cracking 47 29 43 Pass F 6-7 >160 >160 No
Cracking 48 38 41 Pass HB 7 >160 >160 No Cracking 49 51 42
Pass HB 7.3 >160 >160 No Cracking 50 69 43 Pass B 7.3 >160
>160 No Cracking 51 17 48 Pass F 7 >160 >160 No Cracking
52 38 45 Pass B 7.3 >160 >160 No Cracking 53 69 61 Pass 2B
7.6 >160 >160 No Cracking 54 29 16 Pass H 2-3 >160 >160
No Cracking 55 49 19 Pass F 4 >160 100 10 mm Cracking 56 79 20
Pass HB 6 80 8 62 mm Cracking
__________________________________________________________________________
The crystalline polymers impart a more rapid build-up of mechanical
properties to the coatings during fusion compared to currently used
commercial resins. They also tend to give higher physical
properties in thicker films, as shown in the following
examples:
__________________________________________________________________________
Resin Used In Cure Time (Min.) Thickness Impact (inch/lbs) Ex.
Formulation At 163 .degree. C. (m) Front Reverse Flexibility
__________________________________________________________________________
57 Commercial Resin 15 58 8 <2 Cracking All Along 58 having
molecular 30 53 32 2 Cracking All Along 59 wt. of 1800 and 45 49 60
4 33 mm Cracking hydroxyl No. of 59 60 Polyester of tere- 15 51 16
<2 No Cracking 61 phthalic acid, 50 30 47 >160 >160 No
Cracking 62 mole % 1,6-hexane- 45 51 >160 >160 No Cracking
diol and 50 mole % 1,4-butanediol
__________________________________________________________________________
It can be seen that the formulation according to this invention
achieves maximum physical properties between 15-30 minutes, while
that based on the commercial resin only gives maximum properties
after 45 min.
In the following examples, the polyester is derived from
terephthalic acid. The glycols are 1,6-hexanediol and as
indicated.
______________________________________ Melt Viscosity Softening
Hydroxyl Mol. (cps at Range .degree.C. Ex. Glycols No. Wt. 160
.degree. C.) (D.S.C.) ______________________________________ 63 25
mole % ethylene 36 1,800 685 64-140 glycol 64 50 mole % ethylene 44
1,500 927 80-140 glycol 65 25 mole % neo- 63 960 316 80-130 pentyl
glycol 66 50 mole % neo- 47 1,570 2,319 -- pentyl glycol 67 22 mole
% 1,4- 71 970 474 92-150 cyclohexanedi- methanol 68 22 mole %
cyclo- 41 1,800 1,160 100-160 hexanedimethanol 69 30 mole % cyclo-
61 1,260 740 100-134 hexanedimethanol 70 43 mole % cyclo- INSOL
1,160 -- 160-192 hexanedimethanol
______________________________________
For comparison, three commercial thermoset polyesters have the
following properties:
______________________________________ Melt Viscosity Ex. Resin
Molecular Wt. Hydroxyl No. (cps at 160.degree. C.)
______________________________________ 71 X 2,400 56 >10,000 72
Y 1,850 59 6,700 73 Z 2,700 62 >10,000
______________________________________
The following formulations G, H and I are polyesters of
terephthalic acid and 1,6-hexanediol, containing respectively as a
second glycol 22 mole % 1,4-cyclohexanedimethanol, 25 mole %
neopentyl glycol and 25 mole % ethylene glycol. The molecular
weights of the resins used in Formulations G, H and I are 970, 960
and 1800 respectively.
______________________________________ Crystalline Resins in Primer
Surfacer Formulations Parts by Weight G H I
______________________________________ Resin From Ex. 67 74.3 -- --
Resin From Ex. 65 -- 76.4 -- Resin From Ex. 68 -- -- 85.0
Caprolactam-Blocked 25.7 23.6 15.0 Isocyanate Filler 90.0 90.0 90.0
Polymerized Debutanized 5.0 5.0 5.0 Hydrocarbon Resin Flow Modifier
1.0 1.0 1.0 Volatiles Release 0.5 0.5 0.5 Agent Titanium Dioxide
10.0 10.0 10.0 ______________________________________
In the following examples, Formulations G, H and I are used in
primer surface application. Fusion time is 45 minutes and the
fusion temperature is 163.degree. C. In Examples 74-76, Formulation
G is used; in Examples 77-80, Formulation H is used; and in
Examples 81-83, Formulations I is used.
__________________________________________________________________________
Thick- Orange Impact Resistance ness 20.degree. Peel Pencil Peel
Front Reverse Ex. m Gloss Adhesion Hardness Rating (in. lbs.) (in.
lbs.) Flexibility
__________________________________________________________________________
74 27 30 Pass HB 6 >160 >160 No Cracking 75 42 28 Pass HB 6-7
>160 >160 No Cracking 76 64 24 Pass HB 7 >160 >160 No
Cracking 77 20 41 Pass F 4 >160 >160 No Cracking 78 33 44
Pass HB 5 >160 >160 No Cracking 79 54 44 Pass HB 6-7 >160
>160 No Cracking 80 70 42 Pass HB 6-7 >160 >160 No
Cracking 81 26 54 Pass HB 6 >160 >160 No Cracking 82 40 55
Pass HB 6-7 >160 >160 No Cracking 83 66 55 Pass B 7.1 >160
>160 No Cracking
__________________________________________________________________________
Examples 84-96, based on the formulations given in the following
table, demonstrate the coating properties of powder top coats based
on crystalline polyesters. Fusion time and temperature for Examples
84-88, 89-92 and Examples 93-96 are 20 minutes, 163.degree. C.; 5
minutes, 180.degree. C. and 10 minutes, 180.degree. C.,
respectively.
______________________________________ PIGMENTED POWDER TOPCOAT
FORMULATIONS BASED ON CRYSTALLINE THERMOSET POLYESTERS Parts by
Weight Component J K L M ______________________________________
Resin Y 80 -- -- -- From Ex. 4 -- 76.7 -- -- From Ex. 8 -- -- 76.7
-- From Ex. 11 -- -- -- 71.4 Plasticizer 5 5 5 5 Flow Modifier 1 1
1 1 Volatile Release 0.5 0.5 0.5 0.5 Agent Titanium Dioxide 50 50
50 50 Crosslinking Agent 20 23.3 23.3 28.6
______________________________________
__________________________________________________________________________
Impact Thick- Peel Pencil Appearance Resistance ness Gloss Ad-
Hard- Acetone Orange Front Reverse Ex. um 20.degree. hesion ness
Resistance Peel in/lbs in/lbs Flexibility Formulation
__________________________________________________________________________
84 29 45 Pass F Slight 6-7 >160 >160 No Cracking J Break-Up
85 64 55 Pass HB Slight 7.4 >160 100 17 mm Cracking Break-Up 86
48 75 Pass 2B Slight 7.1 >160 >160 No Cracking K Softening 87
52 85 Pass 2B Slight 7.5 >160 >160 No Cracking L Softening 88
55 85 Pass 2B Slight 7.7 >160 >160 No Cracking M Softening 89
52 25 Pass HB Swelling 7.4 40 2 40 mm Cracking J 90 42 33 B Pass
Slight 7.3 20 <2 40 mm Cracking K Softening 91 41 74 Pass B
Slight 7 >160 >160 No Cracking L Softening 92 48 74 Pass B
Slight 7.7 >160 >160 No Cracking M Softening 93 48 26 Pass HB
Slight 7.4 >160 >160 2 mm Cracking J Softening 94 61 46 Pass
B Slight 7.6 >160 >160 No Cracking K Softening 95 36 65 B
Pass Slight 7 >160 >160 No Cracking L Softening 96 36 69 Pass
B Very Slight 7.7 >160 >160 No Cracking M Softening
__________________________________________________________________________
When used in powder topcoat formulations, cured for 20 min. at
163.degree. C., the crystalline polyesters, gave coatings having
excellent physical properties, low orange peel and a significantly
higher gloss than that obtained for the commercial resins. The same
pattern is maintained on cure at 180.degree. C./10 min. The high
gloss finish characteristic of the crystalline resins is believed
to be due to their outstanding flow properties, imparted to the
coatings by virtue of the low melt viscosity of these polymers.
Hydroxyl number is a conventional, well-known term, meaning the
number in terms of milligrams of potassium hydroxide per gram of
sample, over and above the amount required to neutralize any acid
groups that are present.
Number average molecular weight (used herein) is also a
conventional term, and is determined by the well-known technique of
vapor pressure osmometry.
Viscosity is determined in centipoises at specified temperatures
using a conventional Shirley-Ferranti Viscometer at a shear rate of
563 sec.sup.-1.
Unless otherwise specified, all parts, percentages, ratios, etc.,
are by weight.
The invention has been described in detail with particular
reference to certain preferred embodiments thereof but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *